AIR POLLUTION – MONITORING MODELLING AND HEALTH

Monitoring Studies of
Urban Air Quality in Central-Southern
Spain Using Different Techniques
3
Florentina Villanueva, José Albaladejo, Beatriz Cabañas,
Pilar Martín and Alberto Notario
Castilla La Mancha University
Spain
1. Introduction
In urban areas, emissions of air pollutants by anthropogenic processes such as traffic,
industry, power plants and domestic heating systems are the main sources of pollution
(Fenger, 1999). The massive growth in road traffic and in the use of fossil fuels during the
last decades has changed the composition of urban air, increasing the frequency of pollution
episodes and the number of cities experiencing them. The main pollutants monitored in the
atmosphere in these areas are ozone (O 3 ), nitrogen oxides (NO x ), sulphur dioxide (SO 2 ),
carbon monoxide (CO), aromatic compounds and particulate matter. While CO, NO and
aromatic compounds are mainly emitted by traffic, O 3 and NO 2 are originated by
photochemical reactions.
The high levels of solar irradiation observed in the Mediterranean countries favour, in
general, the enhanced photochemical production of secondary oxidising pollutants,
including O 3 , nitrogen dioxide (NO 2 ), and peroxyacetylnitrate (PAN). Amongst these, the O 3
and the nitrogen dioxide (NO 2 ) are capable of causing adverse impacts on human health
and the environment (Lee et al., 1996; WHO, 2000a; Mazzeo and Venegas, 2002, 2004).
Nitrogen dioxide is considered to be an important atmospheric trace gas pollutant not only
because of its effects on health but also because (a) it absorbs visible solar radiation and
contributes to impaired atmospheric visibility, (b) as an absorber of visible radiation, it
could play a potentially direct role in the change in the global climate if its concentrations
were to become high enough (WHO, 2000a), (c) it is one of the major sources of acid rain
(Tang and Lau, 1999), (d) it is, along with nitric oxide (NO), a chief regulator of the oxidising
capacity of the free troposphere by controlling the build-up and fate of radical species,
including hydroxyl radicals, and (e) it plays a critical role in determining concentrations of
O 3 , nitric acid (HNO 3 ), nitrous acid (HNO 2 ), organic nitrates such as PAN (CH 3 C(O)O 2 NO 2 ),
nitrate aerosols and other species in the troposphere. In fact, the photolysis of nitrogen
dioxide in the presence of volatile organic compounds is the only key initiator of the
photochemical formation of ozone and photochemical smog, whether in polluted or
unpolluted atmospheres (WHO, 2000a; Varshney and Singh, 2003). Therefore, ozone mainly